Feeling Clammy

[Minnesota Nice]

Found by a friend 20 miles north of Malta in Montana. I am thinking Bear Paw Shale formation in the Montana Group....reminds me of a joke i will post a little later....

[Minnesota Nice]

Bear Paw Shale Formation....So this bear walks into a bar with his hand all bandaged up and says......I'm looking for the man who shot my paw 

[fifbrindacier]

Oooooh, good joke.

I found a link to a thread of that forum that might interest you : http://www.thefossilforum.com/index.php?/topic/17063-clams/

So, it might be a Arctica ovata.

[sdsnl]

It looks like an elongated shell, I would guess it is in the family Pharidae.

[Ridgehiker]

Its an Unio clam from freshwater (terrestrial) sediments.  Fairly common in the adjacent latest Cretaceous or earliest Paleocene deposits in the Malta area.  These were from freshwater rivers emptying into the Bearpaw Sea (marine).

 

This is a good find when looking for dino remains.  It is easier to spot these white specimens and other molluscs such as Viviparous gasropods than it is to spot the dino remains.  Unios often also indicate productive microvertebrate sites (croc, turtle, raptor teeth, etc). 

 

Not a rule, but in general freshwater molluscs in the Late Creatceous tend to have a softer finish than marine specimens. Less 'shine'. Also, less variety of molluscs are found in a layer. 

 

Anyways, good find. If you come across a bunch of these be sure to look for predation marks. We find specimens with distinct raptor bite marks and have found a tooth in one.

 

Photo of puncture

 

 

[Minnesota Nice]

3 hours ago, Canadawest said:

Photo of puncture

 

 

OK....THAT picture is awesome. Thanks for the ID. I found several Unio in Index Fossils of North America...not sure if I can narrow it down to species given the quality of my piece.  I hope to be in the Malta area this spring. Thanks for the heads up on the Vert possibilities in the area. I note that the Judith River formation is exposed in a lot of the creek and river topography in that area. PM me if you care to share any locals!  

[Ridgehiker]

I like that 'index' book and have used it for decades.

 

 best not to get too caught up in the fossil freshwater species found in western North America.  A deposit of fossil molluscs in just about any locale will be unique and a new species (if they were studied).  

 

Unio clams still are common in rivers in North America. We have 'modern' unios in the rivers that run through the badlands.  Our collecting friends in Tennessee and Kentucky will be familiar with this group of bivalves as they have an extensive list of modern species.

 

Heres an older page showing some associated fossils.

 

http://www.geocities.ws/joe2nora/fm.html

 

 

[Minnesota Nice]

21 hours ago, Canadawest said:

Its an Unio clam from freshwater (terrestrial) sediments.  Fairly common in the adjacent latest Cretaceous or earliest Paleocene deposits in the Malta area.  These were from freshwater rivers emptying into the Bearpaw Sea (marine).

@Canadawest Question for you... is it more likely that this was in the Judith River Formation rather then the Bear Paw? 

[Ridgehiker]

2 hours ago, Minnesota Nice said:

@Canadawest Question for you... is it more likely that this was in the Judith River Formation rather then the Bear Paw? 

 

This is non marine so 'sort of' Judith River.  If found not far from Malta then a chance it is Hell Creek Formation.  The terms Bearpaw and Judith River are a bit broad. There was a huge shallow inland sea (Bearpaw) and this expanded and retracted hundreds of  times during the Late Cretaceous. Most fossil sediments are found in delta areas where rivers flowed into the sea. 

 

There is also some overlap of terms Bearpaw, Pierre Sea, etc.  This depends on what was happening in the Cretaceous at a specific time.  It gets more complicated with broad terms like  Belly River group...Colorado Group, etc.

 

Anyways, as geology becomes more precise...general terms are used less and more specific formation and member names used. 

[Minnesota Nice]

7 minutes ago, Canadawest said:

 

This is non marine so 'sort of' Judith River.  If found not far from Malta then a chance it is Hell Creek Formation.  The terms Bearpaw and Judith River are a bit broad. There was a huge shallow inland sea (Bearpaw) and this expanded and retracted hundreds of  times during the Late Cretaceous. Most fossil sediments are found in delta areas where rivers flowed into the sea. 

 

There is also some overlap of terms Bearpaw, Pierre Sea, etc.  This depends on what was happening in the Cretaceous at a specific time.  It gets more complicated with broad terms like  Belly River group...Colorado Group, etc.

 

Anyways, as geology becomes more precise...general terms are used less and more specific formation and member names used. 

Wondering if you can point me to a resourse that gives an indepth treatment of this areas formations?